Fibronectin receptor structures in the VLA family of heterodimers

Abstract

Multiple cell surface proteins of relative molecular mass 115,000–155,000 (M_r 115K–155K) have been implicated as receptors mediating adhesion to extracellular matrix proteins^1–16. But the organization and relatedness of these peptides has remained unclear. In separate studies, the 'very late antigens' VLA-1 (M_r 210K/130K) and VLA-2 (M_r 160K/130K) were initially characterized as surface heterodimers appearing 2–4 weeks after in vitro stimulation of human T cells^17–19. Three more VLA heterodimers have since been discovered, which, like VLA-1 and VLA-2 (refs 18,20,21), are each composed of unique α-subunits in association with a common 130K β subunit²². This paper shows that the common VLA β-subunit is equivalent to subunits found in structures with known fibronectin and laminin receptor activity^9–12, and that VLA-3 and VLA-5²² are similar or identical to these previously defined receptors for adhesion molecules. Antibody blocking studies confirmed that at least some of the widely distributed VLA proteins of previously unknown function are involved in cell adhesion to fibronectin and laminin. We suggest that the VLA family of receptors may provide cells with multiple independent substrate adhesion capabilities.